1. Field of the Invention
This invention relates to working out production start plans as to when and of what product item to start production in a production process, in which a plurality of different product items are produced.
2. Description of the Prior Art
Recently, it is an increasing trend to produce a plurality of different product items A1, A2, A3, A4, . . . in the same production process. Actually, such circumstances occur frequently that greater burden is imposed on an operator for producing the product item A1 while the burden is less for producing the product item A2. In such cases, it is often undesirable to formulate such a production start plan as to first produce the product items A1 continuously and start continuous production of the product items A2 after producing a necessary quantity of the product item A1. Japanese Laid-Open Patent Publication No. 3-26448 discloses a technique of working out a desired production start plan under such circumstances as noted above. In this technique, when producing the product item A1 in quantity B1, the product item A2 in quantity B2 and the product item A3 in quantity B3 in the same production process, a production start sequence is worked out in which the production start intervals between adjacent ones of the successively produced same kind of product items are as uniform as possible. To this end, such a mathematical means is adopted as to obtain appearance trend values from the production quantities B1, B2, B3, B4, . . . and determine the production start sequence from the obtained appearance trend values. This means can level the operator's burden.
The prior art production start plan work-out method aims at leveling the operator's burden. However, the operator's burden is leveled without knowledge of when and of what product item the shipment is to be made during a period of continuation of the leveled production activity. Therefore, an excessive or insufficient stock situation takes place chronically. In other words, the prior art production start plan work-out method pursues only the easiness of production, and this rather leads to a likelihood of spoiling the economy of the production process.